function check(){
	
	var content = document.getElementById("search").value;
	if(content != ""){
		content = "";
	}
	
}

function addListener(element,e,fn)
{
	if(element.addEventListener){  
		element.addEventListener(e,fn,false);  
		}else{
			element.attachEvent("on" + e,fn);  
        }  
  	}  
    var myinput = document.getElementById("search");  
	    addListener(myinput,"click",function(){  
	    myinput.value = ""; 
    })  
	    addListener(myinput,"blur",function(){  
	    myinput.value = "按帖子内容搜索";  
   }) 
               